1. Field of the Invention
The present invention relates to a method and to apparatus for controlling the transmission ratio of a continuously variable transmission for a motor vehicle.
2. Description of the Related Art
One form of a continuously variable transmission is described in German Patent Publication No. DE 19 546 294 A1. A continuously variable transmission generally includes pairs of conical sheaves in the form of a pair of input sheaves and a pair of output sheaves. Each pair of sheaves includes an axially displaceable sheave and an axially stationary sheave to allow adjustment of the transmission ratio. Between the two pairs of sheaves is an endless, torque-transmitting member in the form of a drive belt for transmitting torque
During the time of operation of such a transmission, changes caused by wear occur, or changes that, for example, are attributable to the transmission itself. Other changes generally occur in transmissions once test-stand-derived parameter settings are changed. As a result, and depending on the duration of operation of a transmission, on wear condition circumstances, and the like, different demands are imposed, and those conditions can adversely influence the regulation accuracy and the operational behavior of the transmission.
An object of the present invention is to provide a method and an apparatus for regulating the transmission ratio of a continuously variable transmission, especially such a transmission intended for use in a motor vehicle, and to provide high operational performance of the transmission over long operating times.